Ore classifier



Dec. 18, 1934. "r. A. DICKSON 1,984,362

ORE CLASSIFIER Filed y 1, 1931 6 Sheets-Sheet l faraway? T. A. DICKSON ORE CLASSIFIER Dec. 18, 1934.

Filed July 1, 1931 6 Sheets-Sheet 2 De. 18, 1934. T. A. DICKSON 1,984,362

ORE CLASSIFIER Filed July 1, 1951 6 Sheets-Sheet 3 1222 8721301" y Z7zelzs'mz v flt'z'oraeys Q $5555 mach T. A. DICKS ON ORE CLASSIFIER Dec. 18, 1934.

Filed July 1, 1931 6 Sheets-Sheet 4 I 2 Vania! Dec. 18, 1934. T. A. DICKSON 1,984,362

ORE GLASSIFTER Filed July 1, 1951 v 6 Sheets-Sheet 5 J72 Wen-Z011 7780 v 0 11 z'eksa 72 B y 7 W T. A. DICKSON ORE CLASSIFIE'R Dec. 18, 1934.

Filed July 1, 1931 6 Sheets-Sheet 6 22061228 .Z7z'caarz,

STATEE 03E CLASSE'HER Thomas A. Dickson, Denver, (Colo, customer to Coloradolron Works Company, mienver, Colo... a corporation of Maine Application July 1, limit, Serial No. .iflfififi 13 mail-us. lei.

This invention relates to improvements in classifier, although it is else applicable to other method of classifying ores and the like and int-- types, us on example of which I show a reciprocatprovements in classifiers. ling relic clusslfier.

It has for its principal object increasing the i have chosen for illustration and description a capacity of s. unit of o. given size and at the some classifier having two helixes within the same 5 time improving the sharpness of the separation tools, end with the lower ends or the helixes between the two products by an improved method deeply submerged. These features favor large of operation. I capacity and high efficiency, end at the same time During the past few years there has been a permit my improvements to be clearly shown in lo continually increasing demand for larger and the drawings. However, I slsoshow an upplicallurpcr grinding units, particularly in ore treettion to e. helical classifier having a single helix. merit plants; and as classification in closed circuit lln the drawings, which are purely diagramwith the grinding mills has become almost the emetic in character, and in which the transverse universal practice, the demands upon the classi views are not true cross sections, but are modified is her have become more dlfilcult to meet in a. single for the sake of clesrness, l u'iechhie oi e. size suitable for direct coupling with Figure l is a. longitudinal section of one term grinding mill. oi spparstus embodying myinvention, showing he s result oi this the grinding-classifying pipes B1 with closed ends sndleterol perforations. operation is e. compromise between the various Flo. 2 is o section substantially on line 2-2 doctors such as capacity, sharpness of separation, oi Fig. l. 20 density of the pulp, etc, and improvement of oily s- 3 i8 e a y w Similar to EI- 1 oi these factors will improve the general result. of a. modified term of the invention, in which .it is well known that good separation by classiwater is introduced through nozzles W. llcutlon requires a. relatively thin pulp and that iilis a sectional w substantially (in line 5 to promote free settling in the classifier it is the of 3. custom to edd at large amount or water to the. o-51s a tudi a s tion 0! a form f my mill discharge. However, pulps thin enough to invention adapted for recirculation of a portion classify most efiectlvely ore undesirably thin for of the thin pulp p s Over the We fiotoiiou, and us a consequence the flotation must i 6 i a ramm ic transverse view of this be carried out upon s pulp which is either poorly form. Substantially OH 11118 O 5. 30 classified or too thin for best results, unless thick= s a tud a Section of a further enirlg utter classification is resorted to. form of the invention in which a portion of rela- Solids suspended in water undergo settling in t v lv t in pu p f r i at n and thinni such it manner thet the density of the pulp as a. is passed through the weir. i

whole as well as the size oi the particles increase Fig. 3 shows a form similar to that oiFig. 7 35 progressively from the surface to the bottom, and in which the thin pulp is reintroduced beneath the. function of a. mechanical classifier is to perthe sands near the upper e d of t P to W s unit the escape of the hue over a weir and by out the fines and to secure sharper separation. means oi a reciprocating rake, chain dragged Fig. 9 is a transverse diagrammatic view subrake, or rotating helix, to remove the coarse from stantially on line 9-9 of Fig. 8. 40 the pool, advance it over an upwardlyinclined Fig. 10 shows a form in which the thin pulp surface and discharge itin a. drained condition. is withdrawn through the weir and reintroduced In a. classifier of the type of Patent Number bymeans of a. pipe inside the tank between the 992,629 to Aklns; the coarse portion, technically helixes. as shown also in Fig. 11 which represents known as the "sands is subjected to a rolling a transverse view substantially on linen-11 of 45 and plowing action whereby the moisture which Fig. 10.

' drains back to the pool serves to largely free Fig. 12 shows a form in which withdrawal is the sands from entrained fines thus returning effected at the Side Of the tank.

- them to the pool where they will have another 13 is a sectional w of y invention anpportunity t be carried over t wait. The plied to a classifier having a single helix. 50 operation of a classifier 0! this type moreover, is Figs- 14 and 15 Show the invention pp d to free from the surges over the weir always present a reciprocating rake a s fi in the classifiers using reciprocating rakes, and Figs. 16 and 17 are longitudinal and transverse for these reasons I show and describe as preferred S ctions of a form of the invention in which the embodiments of my present invention a, helical thin pulp is reintroduced by spraying it upon the 55 sand at the emergence of the sand from the pool.

When a classifier is working well within its capacity the adjustments of speed, inclination of the machine, etc., permit of very sharp separatlon between the sand and slime products; but in modern practice machines are usually forced to the limit of capacity with the full range of the adjustments exhausted, thus necessarily sacrificing the quality of the work performed.

As capacity is forced, one of the first results is the increasing proportion of undesirably coarse material passing over the weir with the slime,

and I have found that this is largely-due to the formation and persistence of a zone within the pool near the overflow weir which I shall now proceed to describe.

It is well known that a relatively thick mixture of solids and liquid acts in a manner similar to a homogeneous liquid of high specific gravity with respect to its ability to hold bodies heavier than water in suspension. The presence of such a mixture in a classifier greatly interferes with the separation by impeding the free settling of the larger particles.

' Referring to the drawings, Fig. 1 shows a classifier in longitudinal section, in which the feed enters at C1, the finer particles are retained in the flow near the surface, represented by Y, Y, and pass over the weir, E1, and the coarser particles or sands, indicated Z, Z, Z, settle to the bottom and are continuously removed by the helix Di shown diagrammatically.

When a classifier has been in operation a short time under conditions which usually accompany attempts to secure a relatively dense overflow, a zone of coarse material or sands forms, of a size and shape which vary with the conditions, as roughly indicated at X, X. This is the result of a thickening action, as distinguished from a classifying action. It is much denser than Y, Y,

and any coarse particles or sands tending to settle from Y are retarded. The indefinite line of separation between X and Y rises until some of the coarse particles from X are carried over the weir by the general flow of Y.

My present invention consists of means for substantially eliminating the above described interfering zone, X, and this I accomplish by the introduction of water at one or more suitable points to thin the mass. Such means may be pipes as indicated at B1, B1, B1, in Figures 1 and 2 for example, the pipes being closed at their inner ends and perforated in a suitable manner such as shown, to direct the water into the thickened pulp zone X. The water so introduced rises, carrying fine solids with it, and also thins the material so that the coarser solids can settle to the 1 bottom. Alternatively, the water may be introduced under appropriate pressure through nozzles passing through the end wall of the tank and weir as indicated at W3, W3, W3, in Figs. 3 and 4. Little water is needed to keep the material in zone X sufficiently thin, and if thisis taken from the water which would otherwise be added to the grinding mill discharge, no thinning of the classifier discharge as a whole takes place, but the machine is caused to make a sharper separation of a larger tonnage, and in some cases with an increase in the density of the overflow product. Nevertheless, there also are cases where the improved results warrant the thinning of the pulp by introducing water additional to that which would otherwise be supplied.

Thinning of the pulp in certain zones being what is necessary, I have found that the actual introduction of additional water can generally be avoided and a similar thinning result obtained by transferring thin pulp from one part of the classifier tank to another part where the pulp is too thick; thereby maintaining the highest possible density as a whole while maintaining locally suitable conditions for eflicient separation of coarse from fine. In describing ways and means of applying such modifications of my invention I shall at the same time point out local conditions other than those described in connection with Fig. '1, and indicate how they can be corrected.

Fig. 5 indicates a way of circulating thin pulp whereby the zone X, X, is kept down well below the weir, E5. In this, a portion of the finished overflow product passes by means of pipe F5 through the pump, P5, driven by means not shown, and reenters the settling pool through jets B5 directed towards the weir E5, the balance of the finished overflow product passing from H5. This is shown also in Fig. 6. The double helix is shown at D5.

The embodiment just described has the effect of increasing the overflow over the weir by the amount of pulp circulated by the pump. Where this would be detrimental, the pump suction may be connected as indicated in Fig. 7, where the pulp is withdrawn through a slot, G1, below the edge of the weir. Here there is no opportunity for the material indicated by X, X, to pass over the weir, as it is withdrawn through the slot, G1, as it rises to that level, and the vertical space between the slot, G7, and the edge of the weir offers a less disturbed settling zone by reason of the slower current near the surface in the part of the pool adjacent to the weir. In this case the finished overflow product passing over weir E1 and discharged at Hz, is kept separate from the thin pulp passed through slot G7, pipe F1, pump P1, and reintroduced through jets B1. The helixes are indicated at D7.

Fig. 8 shows a classifier with lines dividing it into sand draining, sand cleaning, feed and settling, and overflow product zones in which fairly distinct actions take place, and although these will be referred to as there indicated, it will be understood that there is no sharp line of separation between them, and also that they will vary in relative length in different cases according to the proportions of coarse and fine solids, of solids to liquid, etc.

Referring now to Fig. 8, it will be seen that in the sand cleaning zone the sand is embedded not in clear water, but in pulp, and will be discharged carrying, a small amount of fine solids which should be in the overflow product.

I am aware that it is known to introduce water at this point to wash out such fines from the sand, but this is so generally objectionable that his rarely done.

I have found that when such fines in the sand productreach an important amount it is due in great measure to the fact that the pulp separated from the sand is not free to flow toward the lower end of the classifier, but is impeded by the incoming feed, and that there is an actual increase in density (a thickening) in the pool above the feed inlet. The sand product is therefore wet with this pulp which is denser than that in the overflow product zone.

To correct the condition just described I withdraw some of the pulp from a part of the classifier where it is thinnest and re-introduce it under the sands near the upper end of the pool, whereby the sands are stirred up and washed with the relatively thin pulp, and the flow of liquid toward the weir is so increased that it does not thicken. The finally settled sand is then wet with a mixture containing less solids in proportion to water, and the sand product thereby improved.

Fig. 8 and Fig. 9 show the thin pulp withdrawn as described in connection with Fig. 7 and introduced through the bottom of the tank by means of a perforated discharge pipe transverse to the tank as shown at Js. through slot G3 in the weir Es into a compartment Ma separate from and within the chamber Na for the finished overflow product, which flows over the top of weir Ea in chamber Na and out through discharge H8. The withdrawn pulp 'in chamber Ms'iS passed laterally through pipe Fe into pump Pa and thence to pipe Ja. Feed and helixes are indicated at Cs and De. I

Fig. 10 and Fig. 11 show the thinning pulp withdrawn in a similar manner through the slot G10 in the weir Em into separate chamber Mugabove which is disposed the finished overflow product chamber N10 with the outlet Hm. The withdrawn thinning pulp passes from chamber Mm through pipe F10 to pump P10 and is pumped through pipe J10 longitudinally disposed between the helixes inside of the tank, and perforated as shown at its inner and upper portion to discharge the thinning pulp beneath the sands. Feed and helixes are indicated at C10 and D10. 1

In Fig. 12 is shown a form in which the thinning pulp is withdrawn through the side of the tank below the top of the weir E12 as shown by the laterally disposed openings to pipe F12. v The withdrawal is preferably effected from both sides of the tank, providing a discharge pipe F12 at each side delivering thin pulp to the pump Piz from which it is pumped to pipe J12 which may be disposed in the same way as in Fig. 10.

Fig. 13 shows in transverse section an embodiment, similar to that shown in Fig. 8, in which the invention is applied to a classifier having a single helix with the thinning pulp withdrawn at (in and pumped in beneath the sands at J13.

Fig. 14 shows the application of the invention to a reciprocating rake classifien'in which the pulp is withdrawn at the sides at F14, in a manner similar to that shown in Fig. .12, and is pumped by pump P114 to be introduced into the tank beneath the sands at points J14 comprising lateral branch pipes provided, as shown, with discharge apertures or perforations. The application of the invention to a reciprocating rake classifier also is shown diagrammatically in transverse view "in Fig. 15 which shows the slot G15 similar to the construction of Figs. 10 and 11.

The transverse views are not true cross-sections on the lines indicated but are diagrammatically modified for the sake of clearness of operation.

Fig. 16 shows a form of the invention in which the thin pulp passes over weir E16 and is discharged at Hm, a portion thereof being drawn off at F16 and passing through pump P16 to pipe Km which is extended upwardly and to a position overlying the sands at the point of emergence of the sands from the pool, at which'point it is provided with openings or perforations, as shown, re-int-roducing the thin pulp into the tank by spraying it upon the'emerged sands. V

Fig. 17 is a transverse view substantially on line 17-17 of Fig. 16, embodying the essential structure and idea of Fig. 16. In Figs. 16 and 17 the helixes are indicated at Dis.

It will be understood that the various modifications of ,my improvements illustrated and de- The pulp is withdrawn scribed herein may be combined; as by the embodiment of both those shown in Fig. 5 and Fig. 8 in the same machine. It will be apparent to those skilled in the art how my improved features and method of operating may be applied to chain drag classifiers or other mechanical classifiers without specific descriptions and drawings of such applications.

' It will be understood that where, for simplicity of illustration, the perforations in the pipes are shown as opening upwardly for the upward discharge of the thin pulp or liquid into the tank,

the invention is not restricted to the upward disposition of the perforations or openings in the pipes. It will be apparent that the pipes may be readily arranged with respect to the tank, so that the perforations or openings face laterally or downwardly as the thin liquid, regardless of the direction of its discharge from the pipes, i. e. whether upwardly or downwardly. will rise through the sand immediately and accomplish the desired effect.

The larger the amount of thin pulp withdrawn and reintroduced the greater will be the velocity of the pulp passing through the overflow product cleaning zone, and control of the quantity of pulp so recirculated provides additional means of regulating the fineness of the particles which will pass over the weir, a relatively coarse overflow product being produced when the volume is large. vention thus not only improves the separation made'by a classifier, but extends the range within which the separation may be made.

All of the foregoing is directed particularly to mechanical classifiers as distinguished from cones,

spitzkasten and similar apparatus also widely used for classification. Nevertheless, my present invention is also applicable to the latter so-called hindered settling classifiers by withdrawing thin pulp from such classifier or from the overflow thereof and utilizing it as the sorting current either wholly or with some water, with avoidance of the excessive thinning of the pulp which necessarily results when such classifiers are operated with water as heretofore.

It will .be understood that where inthe above description or in the drawings, a feature disclosed in connection with one form of the invention is susceptible of use with other forms illustrated, said feature is to be regarded as though particularly disclosed in connection with the said other forms.

I claim:

1. In combination in a continuous classifier, a tank providing asubstantially quiescent pool, means for continuously feeding pulp into said quiescent pool, means for continuously removing the settled solids, a weir for continuously overflowing a fine product comprising liquid with suspended solids from said pool, and means for withdrawing thin pulp and reintroducing it into said substantially quiescent pool, said withdrawn thin pulp comprising a portion of the overflow over said weir, a receptacle beyond said weir to receive the overflow from'said weir, said receptacle having an outlet in its wall for the discharge of the overflow product, and a second outlet for withdrawing said thin pulp to be reintroduced into said pool.

2. In combination in a continuous classifier, a tank providing a substantially quiescent pool, means for continuously feeding pulp into said quiescent pool, means for continuously removing the settled solids, a weir for continue isly. overflowing aflne product comprising liquid with sus- My in- I pended solids from said pool, and means for withdrawing thin pulp and reintroducing it into said substantially quiescent pool, said withdrawn thin pulp comprising a portion of the overflow over said weir, a receptacle beyond said weir to receive the overfiow from said weir, said receptacle having'an outlet in its wall for the discharge of the overflow product, and a second outlet for withdrawing said thin pulp to be reintroduced into said pool, a conduit from said second outlet passing upwardly over the top of the walls of said tank and extending beneath the surface of the pool, said conduit being provided with a discharge a nozzle beneath the surface and directed toward the weir or discharge end of the classifier to keep down the interfering thickened zone of pulp.

3. In combination in a continuous classifier, a tank providing a substantially quiescent pool, means for continuously feeding pulp into said quiescent pool, means for continuously removing the settled solids, a weir for continuously overflowing a fine product comprising liquid with suspended solids from said pool, and means for withdrawing thin pulp and reintroducing it into said substantially quiescent pool, said withdrawn thin pulp comprising a portion of the overflow over said weir, a receptacle beyond said weir to receive the overflow from said weir, said receptacle having an outlet in its wall for the discharge of the overflow product, and a second outlet for with drawing said thin pulp to be reintroduced into said pool, a conduit from said second outlet passing upwardly over the top of the walls of said tank and discharging downwardly into the tank.

4. In combination in a continuous classifier, a tank providing a substantially quiescent pool, means for continuously feeding pulp into said quiescent pool, means for continuously removing the settled solids, a weir for continuously overflowing a fine product comprising liquid with suspended solids from said pool, and means for withdrawing'thin pulp and reintroducing it into said substantially quiescent pool, said weir being provided with an opening therethrough below the upper edge thereof for withdrawing said thin pulp to be reintroduced into said pool, a receptacle beyond said weir to receive said overflow, said receptacle having a discharge outlet, and a separate receptacle for said thin pulp withdrawn through said opening in the weir.

5 In combination in a continuous classifier, a tank providing a substantially quiescent pool, means for continuously feeding pulp into said quiescent pool, means for continuously removing the settled solids, a weir for continuouslyoverflowing a fine product comprising liquid with $11. pended solids from said pool, and means for with drawing thin pulp and reintroducing it into said substantially quiescent pool, said weir being provided with an opening therethrough below the upper edge thereof for withdrawing said thin pulp to be reintroduced into said pool, a receptacle beyond said weir to receive said overflow, said receptacle having a discharge outlet, and a separate receptacle for said thin pulp withdrawn through said opening in the weir, said separate receptacle being disposed below said first named receptacle and outiet for the overflow.

6. In combination in a continuous classifier, a tank providing a substantially quiescent pool, means for continuously feeding pulp into said quiescent pool, means for continuously removing the settled solids, a weir for continuously overflowing a fine product comprising liquid with suspended solids from said pool, and means for withdrawing thin pulp and reintroducing it into said substantially quiescent pool, said weir being provided with an opening therethrough below the upper edge thereof for withdrawing said thin pulp to be reintroduced into said pool, a receptacle beyond said weir to receive said overflow, said receptacle having a discharge outlet, and a separate receptacle for said thin pulp withdrawn through said opening in the weir, said separate receptacle being disposed within said first named receptacle and above the outlet for the overflow.

7. In combination in a continuous classifier, a

tank providing a substantially quiescent pool, means for continuously feeding pulp into said quiescent pool, means for continuously removing the settled solids, a weir for continuously overflowing aflne product comprising liquid with suspended solids from said pool, and means for withdrawing thin pulp said weir having an opening therethrough below the upper edge thereof for withdrawing said thin pulp, a receptacle beyond said weir to receive said overflow, said receptacle having a discharge outlet, a separate receptacle for said thin pulp withdrawn through said opening in the weir, said receptacle comprising a conduit extending along said tank and discharging said thin pulp into the sands at the point of emergence of the sands from the pool.

8. A classifier according to claim 7 in which said separate receptacle is disposed within said first named receptacle, and above the outlet for the said overflow, said conduit extending longitudinally of the tank and providing a portion extending transversely against the bottom of the tank within the sand cleaning zone and provided with an opening disposed to discharge into the tank, the bottom of said tank being provided with an opening receiving the discharge from said conduit.

9. A classifier according to claim '7 in which said separate. receptacle is disposed below said first named receptacle and outlet for the said overflow, said conduit extending into the tank through the weir and extending along the bottom of the tank centrally thereof and inside the tank, said classifier having a pair of coextensive helixes and said conduit being disposed between said helixes.

10. In combination in a continuous classifier, a tank providing a substantially quiescent pool, means for continuously feeding pulp into said quiescent pool, means for continuously removing the set-tied solids, a weir for continuously overflowing a fine product comprising liquid with suspended solids from said pool, and means for withdrawing thin pulp and reintroducing it into said tank, said means for withdrawing thin pulp including a conduit to receive said withdrawn thin pulp, said conduit extending along said tank and discharging said thin pulp into the sands at the point of emergence of the sands from the pool, to wash the fines from the sands and to return the fines to the pool said conduit extending into the tank through the end wall thereof at the fine discharge end of the tank, and extending along the bottom of the tank centrally thereof and inside the tank, said classifier having a pair vof coextending helixes and said longitudinally extending conduit being disposed between said helixes.

11. In combination in a continuous classifier, a

tank providing a substantially quiescent pool,

means for continuously feeding pulp into said quiescent pool, means for continuously removing the settled solids, a weir for continuously overflowing a fine product comprising liquid with suspended solids irom said pool, and means for withdrawing thin pulp and reintroducing it into said tank, said means for withdrawing thin pulp including a conduit to receive said withdrawn thin pulp, said conduit extending along said tank and discharging said thin pulp into the sands at the point of emergence of the sands from the pool, to wash the fines from the sands and to return the lines to the pool said tank being provided with a discharge opening for the thin pulp in its side wall disposed laterally oi the weir, said conduit being in communication with said opening.

12. In combination in a continuous classifier, a tank providing a substantially quiescent pool, means for continuously ieeding pulp into said quiescent pool, means for continuously removing the settled solids, a weir for continuously 'overflowing a fine product comprising liquid with suspended solids irom said pool, and means for withdrawing thin pulp and reintroducing it into said tank, said means for withdrawing thin pulp including a conduit to receive said withdrawn thin pulp, said conduit extending alongsaid tank and discharging said thin pulp into the sands at the point of emergence of the sands from the pool, to wash the lines from the sands and to return the fines to the pool the opposite side walls of the tank adjacent the weir bel lprovided with discharge openings for the thin pulp disposed laterally of the weir, said conduit being in communication with said openings.

13. In combination in a continuous classifier, a

tank providing a substantially quiescent pool,

lower outlet for withdrawing a portion of the thin pulp of the overflow, said weir having an opening therethrough below its upper edge for the passage of thin pulp, and conducting means including a conduit receiving the discharge from said weir opening, and delivering it through the bottom of said tank into the sands'at the sand cleaning zone to wash out the lines, and a conduit receiving the discharge from said lower opening and delivering it through the top of the tank into the top of the pool to thin the interiering zonev oi thickenedjulp near the line discharge end of the tank.

THOMAS A. DICKSON. 

